Cells must control gene expression so that
A) their genes will be expressed only when needed.
B) their genes will always be expressed.
C) their genes will never be expressed.
D) genetic disorders can be corrected.
The correct response is A. In gene expression, the genetic information is translated by protein synthesis into a protein, a functional gene product. However, cells control the expression of genes producing the proteins it needs, when it needs them and allowing for differentiation in the body amongst the various cells contained therein. An example is the hormone insulin, which is a protein vital for the regulation of blood glucose levels. Its expression allows for the excess blood glucose to enter the cells to be utilized in respiration and for the rest to be stored as glycogen. Gene expression allows for hormones to be released when needed, for cyclins which regulate the cell cycle to be produced and for important protein products to be present to adapt to an ever changing environment outside and within a cell.